Pit Road
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pit Road clear sky chart from 2005-11-05 to 2017-09-23.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
29%
14663
12%
46925
8%
14633
35%
14633
16%
33873

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
15%
720
6%
2506
2%
716
20%
716
6%
2069
January16th to endNight
21%
768
11%
2610
5%
768
29%
768
11%
1979
February1st to 15thNight
16%
702
8%
2287
4%
701
23%
701
10%
1800
February16th to endNight
21%
631
12%
1985
5%
631
30%
631
12%
1487
March1st to 15thNight
17%
720
12%
2061
6%
720
23%
720
14%
1589
March16th to endNight
30%
768
18%
2061
9%
768
37%
768
22%
1432
April1st to 15thNight
23%
718
14%
1796
5%
718
28%
718
19%
1336
April16th to endNight
30%
627
17%
1707
8%
627
36%
627
22%
1202
May1st to 15thNight
33%
360
17%
1440
16%
360
42%
360
16%
948
May16th to endNight
34%
375
13%
1497
9%
374
46%
374
18%
941
June1st to 15thNight
36%
360
9%
1440
8%
360
44%
360
16%
936
June16th to endNight
41%
360
9%
1440
13%
360
46%
360
19%
913
July1st to 15thNight
48%
340
14%
1360
18%
340
56%
340
26%
758
July16th to endNight
52%
376
13%
1418
14%
354
57%
354
25%
805
August1st to 15thNight
53%
482
14%
1553
11%
480
56%
480
25%
977
August16th to endNight
52%
675
20%
1821
11%
675
57%
675
35%
1137
September1st to 15thNight
44%
720
14%
1800
7%
720
46%
720
27%
1270
September16th to endNight
47%
689
21%
1887
14%
689
52%
689
31%
1206
October1st to 15thNight
30%
660
16%
1980
11%
660
38%
660
19%
1403
October16th to endNight
24%
704
9%
2172
5%
704
30%
704
11%
1699
November1st to 15thNight
28%
700
16%
2376
13%
700
34%
700
14%
1714
November16th to endNight
20%
720
9%
2520
6%
720
24%
720
9%
1980
December1st to 15thNight
15%
720
6%
2520
3%
720
20%
720
7%
2083
December16th to endNight
14%
768
8%
2688
4%
768
19%
768
7%
2209

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
17%9%37%6%3445%6%31%
47993
Night
17%10%47%6%34445%32%
47095
TransparencyDay
52%6%11%19%9%1
47681
Night
53%5%11%18%9%
46925
SeeingDay
22%12%28%21%10%3
5431
Night
22%11%29%25%9%
14665

By Month

Percentage Cloud Cover NE (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
20%14%5%9%7%24345%20%
1432
16th to endDay
14%15%7%10%8%2433423%
1614
February1st to 15thDay
12%13%6%13%8%35%45%6%20%
1575
16th to endDay
17%14%5%7%5%43446%25%
1488
March1st to 15thDay
16%13%5%7%7%45%43427%
1886
16th to endDay
14%8%5%6%5%24346%39%
2163
April1st to 15thDay
22%12%35%423335%32%
2152
16th to endDay
22%7%26%423346%36%
2260
May1st to 15thDay
20%8%35%5%2435%6%33%
2511
16th to endDay
17%6%36%6%25%5%5%6%34%
2618
June1st to 15thDay
22%6%36%6%3445%6%30%
2520
16th to endDay
16%5%26%5%36%5%6%7%33%
2520
July1st to 15thDay
12%5%246%36%5%6%8%37%
2520
16th to endDay
11%5%25%5%35%6%7%9%36%
2654
August1st to 15thDay
13%6%37%7%35%45%6%36%
2396
16th to endDay
12%5%25%5%35%5%6%9%38%
2369
September1st to 15thDay
18%5%26%424348%39%
2160
16th to endDay
16%5%35%423346%43%
1907
October1st to 15thDay
22%8%26%6%25%435%33%
1650
16th to endDay
28%11%37%6%23435%23%
1700
November1st to 15thDay
15%11%37%434346%34%
1482
16th to endDay
23%15%47%6%4444420%
1440
December1st to 15thDay
19%18%7%10%8%3443415%
1440
16th to endDay
23%18%5%7%6%2334419%
1536
January1st to 15thNight
17%16%7%10%8%4444417%
2506
16th to endNight
14%15%5%8%7%35%445%26%
2610
February1st to 15thNight
12%14%7%11%7%35%5%4421%
2285
16th to endNight
15%12%6%9%7%34445%27%
1985
March1st to 15thNight
18%13%6%7%7%24235%27%
2049
16th to endNight
15%8%36%5%33345%39%
2061
April1st to 15thNight
22%9%36%424345%33%
1796
16th to endNight
19%9%25%424346%36%
1707
May1st to 15thNight
22%8%35%5%23236%36%
1440
16th to endNight
15%5%245%35%447%39%
1495
June1st to 15thNight
19%426%5%3445%7%36%
1440
16th to endNight
16%5%25%435%5%6%7%36%
1440
July1st to 15thNight
11%324336%5%48%46%
1440
16th to endNight
10%4244246%6%9%44%
1514
August1st to 15thNight
9%425%6%35%5%6%7%42%
1563
16th to endNight
9%32442445%8%49%
1821
September1st to 15thNight
16%5%26%5%2445%6%41%
1800
16th to endNight
16%425%422336%49%
1887
October1st to 15thNight
21%8%25%5%2433437%
1980
16th to endNight
25%10%36%5%35%45%5%24%
2172
November1st to 15thNight
19%10%25%6%34446%31%
2376
16th to endNight
22%13%5%9%5%2433424%
2520
December1st to 15thNight
21%17%6%8%6%35%33419%
2520
16th to endNight
23%17%6%9%7%2432418%
2688

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
67%49%12%5%
1433
16th to endDay
65%410%12%6%
1614
February1st to 15thDay
63%7%10%13%4
1577
16th to endDay
60%411%13%8%1
1488
March1st to 15thDay
61%49%16%6%1
1897
16th to endDay
46%410%20%14%4
2163
April1st to 15thDay
54%37%18%12%2
2152
16th to endDay
49%36%20%16%3
2260
May1st to 15thDay
51%48%18%13%2
2511
16th to endDay
48%6%11%19%12%2
2622
June1st to 15thDay
53%6%10%19%9%
2520
16th to endDay
46%7%11%20%12%1
2520
July1st to 15thDay
39%8%13%25%12%
2371
16th to endDay
41%9%15%23%9%
2487
August1st to 15thDay
46%7%14%20%9%
2382
16th to endDay
40%9%16%24%8%
2369
September1st to 15thDay
43%5%13%26%10%
2160
16th to endDay
42%5%12%30%8%
1907
October1st to 15thDay
53%5%11%18%10%
1650
16th to endDay
63%5%11%14%4
1700
November1st to 15thDay
50%7%15%18%7%
1482
16th to endDay
65%6%11%10%41
1440
December1st to 15thDay
72%6%9%9%2
1440
16th to endDay
68%5%10%11%3
1536
January1st to 15thNight
69%6%10%8%4
2506
16th to endNight
60%410%16%7%
2610
February1st to 15thNight
64%5%11%13%4
2287
16th to endNight
58%5%10%17%8%
1985
March1st to 15thNight
60%410%17%6%
2061
16th to endNight
46%5%10%19%16%2
2061
April1st to 15thNight
54%37%18%13%1
1796
16th to endNight
48%38%19%16%2
1707
May1st to 15thNight
51%37%18%15%3
1440
16th to endNight
42%7%13%21%13%2
1497
June1st to 15thNight
46%7%13%22%9%
1440
16th to endNight
43%6%13%20%14%
1440
July1st to 15thNight
32%7%13%28%16%1
1360
16th to endNight
34%7%14%28%13%
1418
August1st to 15thNight
37%8%16%23%12%
1553
16th to endNight
32%7%16%33%10%
1821
September1st to 15thNight
43%7%12%25%10%
1800
16th to endNight
38%413%35%7%
1887
October1st to 15thNight
51%410%20%12%
1980
16th to endNight
60%6%12%14%5%
2172
November1st to 15thNight
53%6%12%17%9%
2376
16th to endNight
64%5%12%14%3
2520
December1st to 15thNight
69%6%10%10%3
2520
16th to endNight
70%49%10%5%
2688

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
25%25%25%21%3
60
16th to endDay
40%12%29%10%6%
77
February1st to 15thDay
27%21%38%11%1
90
16th to endDay
34%22%25%14%3
147
March1st to 15thDay
26%18%32%16%5%
270
16th to endDay
22%17%31%17%10%1
288
April1st to 15thDay
30%20%25%16%7%
270
16th to endDay
28%16%24%18%8%4
270
May1st to 15thDay
32%8%27%18%8%4
288
16th to endDay
19%17%31%20%9%1
331
June1st to 15thDay
28%12%25%22%9%1
315
16th to endDay
14%12%30%27%13%1
315
July1st to 15thDay
12%5%35%29%12%4
305
16th to endDay
11%6%31%30%15%4
326
August1st to 15thDay
17%323%33%13%8%
313
16th to endDay
12%7%27%26%15%10%
332
September1st to 15thDay
20%6%22%19%18%12%
315
16th to endDay
15%9%23%22%18%10%
283
October1st to 15thDay
26%11%26%20%13%
255
16th to endDay
35%13%28%15%6%
261
November1st to 15thDay
18%13%35%21%10%1
136
16th to endDay
38%13%31%11%31
60
December1st to 15thDay
23%16%38%16%5%
60
16th to endDay
37%31%26%4
64
January1st to 15thNight
25%17%31%18%5%
720
16th to endNight
22%13%32%24%6%
768
February1st to 15thNight
18%15%39%21%4
704
16th to endNight
22%16%34%22%4
631
March1st to 15thNight
28%16%30%21%3
720
16th to endNight
18%16%30%23%10%
768
April1st to 15thNight
26%14%30%22%5%
718
16th to endNight
23%13%28%25%8%
627
May1st to 15thNight
26%7%26%28%8%1
360
16th to endNight
16%8%35%28%10%
375
June1st to 15thNight
19%8%31%31%8%
360
16th to endNight
18%7%28%32%12%
360
July1st to 15thNight
10%330%39%15%1
340
16th to endNight
11%327%41%15%
376
August1st to 15thNight
11%323%37%21%2
482
16th to endNight
10%427%36%19%2
675
September1st to 15thNight
19%5%25%27%18%3
720
16th to endNight
19%6%21%28%21%2
689
October1st to 15thNight
25%9%30%22%12%
660
16th to endNight
32%11%27%20%8%
704
November1st to 15thNight
24%12%28%22%11%
700
16th to endNight
30%17%25%20%6%
720
December1st to 15thNight
29%18%30%17%4
720
16th to endNight
32%13%29%18%4
768
Page generated at 2017-09-24 09:15:47. Version ac04

Copyright 2017 A. Danko


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